 /*******************************************************************************
  * Copyright (c) 2007 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  ******************************************************************************/

 package org.eclipse.ui.internal.services;

 import org.eclipse.core.expressions.Expression;
 import org.eclipse.core.expressions.IEvaluationContext;
 import org.eclipse.jface.util.IPropertyChangeListener;
 import org.eclipse.jface.util.PropertyChangeEvent;
 import org.eclipse.ui.ISourceProvider;

 /**
  * @since 3.3
  *
  */
 public final class EvaluationService implements IEvaluationService {
     
     private EvaluationAuthority restrictionAuthority;
     private EvaluationAuthority evaluationAuthority;

     private IPropertyChangeListener restrictionListener = new IPropertyChangeListener() {

         public void propertyChange(PropertyChangeEvent event) {
             IEvaluationReference source = (IEvaluationReference) event
                     .getSource();
             if (source == null)
                 return;
             
             IEvaluationReference mappedReference = source.getTargetReference();
             if (mappedReference == null)
                 return;

             boolean evaluationEnabled = false;
             if (event.getNewValue() != null) {
                 evaluationEnabled = ((Boolean ) event.getNewValue()).booleanValue();
             } else {
                 evaluationEnabled = false;
             }
             mappedReference.setPostingChanges(evaluationEnabled);
         }
     };
     

     public EvaluationService() {
         evaluationAuthority = new EvaluationAuthority();
         restrictionAuthority = new EvaluationAuthority();
     }

     /*
      * (non-Javadoc)
      *
      * @see org.eclipse.ui.internal.services.IEvaluationService#addEvaluationListener(org.eclipse.core.expressions.Expression,
      * org.eclipse.jface.util.IPropertyChangeListener, java.lang.String)
      */
     public IEvaluationReference addEvaluationListener(Expression expression,
             IPropertyChangeListener listener, String property, Expression restrictEvaluation) {
         IEvaluationReference expressionReference = new EvaluationReference(expression, listener, property, null);
         
         evaluationAuthority.addEvaluationListener(expressionReference);
         if (restrictEvaluation != null) {
             IPropertyChangeListener restrictionListener = getRestrictionListener();
             // create a binding from the restriction to the expression
 IEvaluationReference restrictRef = new EvaluationReference(
                     restrictEvaluation, restrictionListener,
                     "evaluate", expressionReference); //$NON-NLS-1$

             // now set the pair in the opposite configuration for later cleanup
 expressionReference.setTargetReference(restrictRef);
             restrictionAuthority.addEvaluationListener(restrictRef);
         }
         return expressionReference;
     }

     /**
      * @return
      */
     private IPropertyChangeListener getRestrictionListener() {
         return restrictionListener ;
     }

     /*
      * (non-Javadoc)
      *
      * @see org.eclipse.ui.internal.services.IEvaluationService#removeEvaluationListener(org.eclipse.ui.internal.services.IEvaluationReference)
      */
     public void removeEvaluationListener(IEvaluationReference ref) {
         evaluationAuthority.removeEvaluationListener(ref);
         IEvaluationReference target = ref.getTargetReference();
         if (target != null) {
             restrictionAuthority
                     .removeEvaluationListener(target);
         }
     }

     /*
      * (non-Javadoc)
      *
      * @see org.eclipse.ui.services.IServiceWithSources#addSourceProvider(org.eclipse.ui.ISourceProvider)
      */
     public void addSourceProvider(ISourceProvider provider) {
         restrictionAuthority.addSourceProvider(provider);
         evaluationAuthority.addSourceProvider(provider);
     }

     /*
      * (non-Javadoc)
      *
      * @see org.eclipse.ui.services.IServiceWithSources#removeSourceProvider(org.eclipse.ui.ISourceProvider)
      */
     public void removeSourceProvider(ISourceProvider provider) {
         restrictionAuthority.removeSourceProvider(provider);
         evaluationAuthority.removeSourceProvider(provider);
     }

     /*
      * (non-Javadoc)
      *
      * @see org.eclipse.ui.services.IDisposable#dispose()
      */
     public void dispose() {
         restrictionAuthority.dispose();
         evaluationAuthority.dispose();
     }
     
     /* (non-Javadoc)
      * @see org.eclipse.ui.internal.services.IEvaluationService#getCurrentState()
      */
     public IEvaluationContext getCurrentState() {
         return evaluationAuthority.getCurrentState();
     }

     /* (non-Javadoc)
      * @see org.eclipse.ui.internal.services.IEvaluationService#addServiceListener(org.eclipse.jface.util.IPropertyChangeListener)
      */
     public void addServiceListener(IPropertyChangeListener listener) {
         restrictionAuthority.addServiceListener(listener);
         evaluationAuthority.addServiceListener(listener);
     }

     /* (non-Javadoc)
      * @see org.eclipse.ui.internal.services.IEvaluationService#removeServiceListener(org.eclipse.jface.util.IPropertyChangeListener)
      */
     public void removeServiceListener(IPropertyChangeListener listener) {
         restrictionAuthority.removeServiceListener(listener);
         evaluationAuthority.removeServiceListener(listener);
     }
 }
